This project involves several approaches to the problem of understanding the mechanical aspect of the contractile mechanism of smooth muscle, using female rat (uterus) and rabbit (mesotubarium superius and ovarian ligament) reproductive smooth muscles as model preparations. Mechanical interventions, especially minute sinusoidal oscillations superimposed on large controlled linear streches, will be used to probe intact muscle preparations during isometric and isotonic contraction and relaxation. Elastic and viscous parameters thus determined will be integrated into a consistent conceptual framework intended to provide an experimentally-testable hypothesis of smooth muscle contraction. Similar mechanical experiments will be done on calcium-activated, detergent-treated, muscle preparations (now under development) in order to explore the role of activation in determining muscle mechanical properties. A digital computer simulation will attempt to assemble the various experimental data into a consistent overall picture of the mechanical contractile process.